Any complaint should be specified as fully, clearly and accurately as possible. Recognising that these matters may have taken place up to three decades ago, it would nonetheless be helpful to the inquiry if complaints could say what was said or done, by whom and against whom, in whose presence or hearing and with what effect, and when and where the incident occurred. If a complaint about the incident was made straight afterwards, then details of that complaint should also be given.
I don't know if I am out of line here, but in my former profession dealing with people who exhibited at times very irate behavior we used standard sheets to report 'incidents'.
Simple questions like: names of people present, names of persons involved, instigator, victim (of any), what was told, short description of events, was it sexual in nature, was it physical, was the police notified, how much on a scale of 1 to 5 does it affect you, have you had an immediate debrief, do you want additional help. And if needed an extra sheet to express what more you want to tell.
if I would report abuse to the governors, I'd make such a sheet for myself (leaving out the cops and debriefs) and keep the facts part as business-like as possible. It would make it easier for them to do reference checks and find the people involved. Otherwise you might start wandering all over the place in long rambling letters when all the emotions come floating to the surface and leave it to the governors to fish the vital information out of it.